Mucosal biopsies from the alimentary canal from patients infected with Norwalk agent will be studied by organ culture over medium containing tritiated thymidine. Radioautographs will be prepared and examined for ectopic incorporation of tritiated thymidine indicative of viral proliferation. Factors influencing incorporation of carbohydrate precursors into glycoprotein and subsequent secretion of newly synthesized glycoprotein will be studied in cultured rectal biopsies from patients with cystic fibrosis, their asymptomatic first order relatives and these will be compared to findings in rectal biopsies from normal volunteers. The fine structure of fetal rodent stomach and colon will be examined by electron microscopy during organogenesis occurring during the last week of gestation. The segments of fetal rodent stomach and small intestine will be maintained in organ culture and the effect of putative substances that may influence organogenesis such as thyroid hormone and epidermal growth factor will be studied in this system. Corticosteroid receptors in fetal rodent stomach and small intestine will be studied during gastric and intestinal organogenesis. BIBLIOGRAPHIC REFERENCES: Trier, J.S.: Diagnostic usefulness of small intestinal biopsy. Viewpoints on Digestive Diseases. Vol. 9, January, 1977. Neutra, M.R., Grand, R.J., and Trier, J.S.: Glycoprotein synthesis, transport and secretion by epithelial cells of human rectal mucosa: Normal and cystic fibrosis. Laboratory Invest, May, 1977, in press.